Exterior insulation and finish systems (EIFS) are multi-layered exterior wall systems that are used on both commercial buildings and homes. EIFS typically comprises the following components: insulation board made of polystyrene or polyisocyanurate foam, which is secured to the exterior wall surface with a specially formulated adhesive and/or mechanical attachment; a durable water-resistant base coat, which is applied on top of the insulation and reinforced with fiberglass mesh for added strength; and a usually textured and durable finish coat typically produced using an acrylic co-polymer technology.
The finish coat composition usually contains in addition to the co-polymer an aggregate that is used for the appearance and durability of the finish coat composition. The coatings used as the outermost layer in EIFS systems are typically supplied in 5-gallon pails that weigh about 70 pounds each. The heavy weight of the pails slows down the productivity of the workers during application of the finish.
To reduce the weight of these finish compositions the aggregate component has been partially replaced with a lighter material to form a lightweight finish. Lightweight finishes utilize naturally occurring aggregates such as perlite, hyperlite, vermiculite, expanded clay and pumice stone. Due to the high porosity, in the prior art these minerals have been coated with silicone to prevent the absorption of water and thickening of the textured finish. However, if the light weight naturally occurring aggregate is not completely coated, shelf life problems can occur due the excessive viscosity of the packaged finish composition.
Therefore, it is desirable to provide a finish composition which is lightweight but does not become excessively viscous after addition of the lightweight aggregate. Additionally, it would be desirable to avoid the extra production step of coating the lightweight aggregate and the reliance on a uniform and complete coating of the lightweight aggregate to avoid substantial thickening of the finish coating.